A Standardized Generalized Dimensionality Discrepancy Measure and a Standardized Model‐Based Covariance for Dimensionality Assessment for Multidimensional Models          下载免费PDF全文

Roy Levy  Yuning Xu  Nedim Yel  Dubravka Svetina 《Journal of Educational Measurement》2015,52(2):144-158

The standardized generalized dimensionality discrepancy measure and the standardized model‐based covariance are introduced as tools to critique dimensionality assumptions in multidimensional item response models. These tools are grounded in a covariance theory perspective and associated connections between dimensionality and local independence. Relative to their precursors, they allow for dimensionality assessment in a more readily interpretable metric of correlations. A simulation study demonstrates the utility of the discrepancy measures’ application at multiple levels of dimensionality analysis, and compares them to factor analytic and item response theoretic approaches. An example illustrates their use in practice.  相似文献   

Fluctuations of DNA mobility in nanofluidic entropic traps     

Lingling Wu  Stephen Levy 《Biomicrofluidics》2014,8(4)

We studied the mobility of DNA molecules driven by an electric field through a nanofluidic device containing a periodic array of deep and shallow regions termed entropic traps. The mobility of a group of DNA molecules was measured by fluorescent video microscopy. Since the depth of a shallow region is smaller than the DNA equilibrium size, DNA molecules are trapped for a characteristic time and must compress themselves to traverse the boundary between deep and shallow regions. Consistent with previous experimental results, we observed a nonlinear relationship between the mobility and electric field strength, and that longer DNA molecules have larger mobility. In repeated measurements under seemingly identical conditions, we measured fluctuations in the mobility significantly larger than expected from statistical variation. The variation was more pronounced for lower electric field strengths where the trapping time is considerable relative to the drift time. To determine the origin of these fluctuations, we investigated the dependence of the mobility on several variables: DNA concentration, ionic strength of the solvent, fluorescent dye staining ratio, electroosmotic flow, and electric field strength. The mobility fluctuations were moderately enhanced in conditions of reduced ionic strength and electroosmotic flow.  相似文献   

Development and recent advances of the techno-graphic arts     

Louis Edward Levy 《Journal of The Franklin Institute》1915

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Assessment of the Learning Environment of Inquiry-Type Laboratories in High School Chemistry     

Avi Hofstein  Tami Levy Nahum  Relly Shore 《Learning Environments Research》2001,4(2):193-207

An inquiry-type laboratory has been implemented into the chemistry curriculum in high schools in Israel. In this study, we investigated the idea that generally the science laboratory provides a unique learning environment that differs from the learning environment that exists in classrooms in which other instructional techniques are used. Moreover, the inquiry laboratory provides students with a learning situation in which they are involved in activities that might influence some of the variables that are influencing the learning environment of such laboratories. In this study, the Science Laboratory Environment Inventory (SLEI) was used to assess the students' perceptions of their chemistry laboratory learning environment. Statistical comparison of two groups (control and inquiry) revealed significant differences between the groups regarding their actual perceptions. Moreover, it was found that the differences between the actual and preferred laboratory learning environment were significantly smaller for the inquiry group than for the control group. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Using action,reflection and modelling (ARM) in Malaysian primary schools: connecting ‘the ARM theory’ with student teachers’ reported practice     

Claire Dickerson  Joy Jarvis  Roger Levy  Kit Thomas 《Teachers and Teaching》2017,23(4):494-514

This article presents Malaysian student teachers’ reports of using an action, reflection and modelling (ARM) pedagogical approach during their placements in Malaysian primary schools. The ARM approach was designed to support the implementation of the Malaysian primary school mathematics curriculum, which involved changing classroom practice in learning and teaching. It was developed and used during a Malaysia–UK collaborative project to construct a Bachelor of Education (Honours) degree programme in Primary Mathematics for a cohort of 120 student teachers in Malaysia. The three principles integral to the ARM approach were repeatedly made explicit to the student practitioners who were engaged in learning and teaching on the new degree programme. Using findings from surveys carried out with the students at the end of their first and final placements, this article provides examples of the way some of them described ARM and recounted how they had used the approach in the classroom. Four of these narratives are used as ‘vignettes’ to illustrate the students’ perceptions of using new ways of learning and teaching in primary schools and to inform and enable a discussion of the relationship between theory and practice in teacher education.  相似文献   

Students' Perceptions of Interpersonal Aspects of the Learning Environment   总被引：1，自引：0，他引：1  

Levy  Jack  Wubbels  Theo  Den Brok  Perry  Brekelmans  Mieke 《Learning Environments Research》2003,6(1):5-36

This study examined variables associated with differences in students' perceptions of interpersonal teacher behavior. The perceptions of 3023 students and 74 teachers in 168 classes in seven secondary schools were used in the analyses. Investigating variance at the student, class, teacher and school levels revealed that several variables are significantly related to students' perceptions: student and teacher gender, student and teacher ethnic background, student age and grade, class size, grade level, subject taught and teacher experience. There were interaction effects between some variables, such as student ethnicity and student gender, as well as student and teacher gender. While significant, the amount of variance explained by these was low (around 10%). The outcomes generally confirmed earlier research, although some new effects were found. Perhaps the main result of the study was its verification of the complex and interactive nature of students' perceptions of the learning environment and researchers' understanding of it.  相似文献   

Dimensionality in Compensatory MIRT When Complex Structure Exists: Evaluation of DETECT and NOHARM     

Dubravka Svetina  Roy Levy 《Journal of Experimental Education》2016,84(2):398-420

This study investigated the effect of complex structure on dimensionality assessment in compensatory multidimensional item response models using DETECT- and NOHARM-based methods. The performance was evaluated via the accuracy of identifying the correct number of dimensions and the ability to accurately recover item groupings using a simple matching similarity (SM) coefficient. The DETECT-based methods yielded higher proportion correct than the NOHARM-based methods in two- and three-dimensional conditions, especially when correlations were ≤.60, data exhibited ≤30% complexity, and sample size was 1,000. As the complexity increased and the sample size decreased, the performance of the methods typically diminished. The NOHARM-based methods were either equally successful or better in recovering item groupings than the DETECT-based methods and were mostly affected by complexity levels. The DETECT-based methods were affected largely by the test length, such that with the increase of the number of items, SM coefficients would decrease substantially.  相似文献   

Using the Internet in teaching: the views of practitioners (A survey of the views of secondary school teachers in Sheffield, UK)   总被引：2，自引：0，他引：2  

Andrew Madden  Nigel Ford  David Miller  Philippa Levy 《British journal of educational technology : journal of the Council for Educational Technology》2005,36(2):255-280

A questionnaire was generated from the results of a series of interviews at The City School one of the 27 state secondary schools in Sheffield. In October 2002, it was sent out to 499 Heads of Department at the remaining 26 state secondary schools. Responses were received from 188 teachers, ranging in age from 24 to 60 years old. The purpose of the questionnaire was to gain information about teachers’ views of the Internet and its usefulness as an educational tool. Nearly 85% of teachers acquired their Internet skills informally (self‐taught, learned from friends/colleagues, etc), rather than on a taught course. Despite this, most of the respondents were confident of their ability to use the Internet, with the most confident users being young teachers of technical subjects. However, there was a widespread perception (particularly amongst women teachers) that students are more competent users of the Internet than are teachers. Older teachers were more likely to feel under pressure to use the Internet than their younger colleagues. Only about a third of teachers agreed with the statement “I often use the Internet with classes.” Responses varied significantly according to school and subject. There was strong support, however, for the suggestion that the Internet is a valuable source of learning and teaching materials.  相似文献   

Virtual child pornography: The eroticization of inequality     

Neil Levy 《Ethics and Information Technology》2002,4(4):319-323

The United States Supreme Court hasrecently ruled that virtual child pornographyis protected free speech, partly on the groundsthat virtual pornography does not harm actualchildren. I review the evidence for thecontention that virtual pornography might harmchildren, and find that it is, at best,inconclusive. Saying that virtual childpornography does not harm actual children isnot to say that it is completely harmless,however. Child pornography, actual or virtual,necessarily eroticizes inequality; in a sexistsociety it therefore contributes to thesubordination of women.  相似文献   

Power in Bayesian Mediation Analysis for Small Sample Research     

Milica Miočević  David P. MacKinnon  Roy Levy 《Structural equation modeling》2017,24(5):666-683

Bayesian methods have the potential for increasing power in mediation analysis (Koopman, Howe, Hollenbeck, & Sin, 2015; Yuan & MacKinnon, 2009). This article compares the power of Bayesian credibility intervals for the mediated effect to the power of normal theory, distribution of the product, percentile, and bias-corrected bootstrap confidence intervals at N ≤ 200. Bayesian methods with diffuse priors have power comparable to the distribution of the product and bootstrap methods, and Bayesian methods with informative priors had the most power. Varying degrees of precision of prior distributions were also examined. Increased precision led to greater power only when N ≥ 100 and the effects were small, N < 60 and the effects were large, and N < 200 and the effects were medium. An empirical example from psychology illustrated a Bayesian analysis of the single mediator model from prior selection to interpreting results.  相似文献